Catalyst manufacturers are continuously seeking catalysts, additives, and processes to improve the properties of catalysts and additives to lower the cost of producing catalysts and additives. Catalyst and additive producers, typically, search for materials, equipment, or processes that decrease the cost of raw materials or utilities, or increase the efficiency of the catalyst process with increased feed through-put, lower equipment maintenance, or improved utilization of raw materials. All these factors contribute to the manufacturing costs of catalysts and additives.
The use of transition metals in specific fluid cracking catalyst formulations can improve the selectivity of a given fluid cracking catalyst unit, using a specific gas oil feed, but results in undesired concentrations of coke and yields of light gas. The undesirable loss of gasoline yield and increases in coke and light gases with transition metal formulations diminishes the value of the enhanced production of desirable products such as olefins.
Rare earth complex oxide combustion catalysts have been proposed in U.S. Pat. No. 5,242,881 to Tang et al. In this patent, perovskite-type rare earth complex oxide active components are carried on a support using mullite as the main phase. In the prior art section of the Tang et al. patent, the use of perovskite-type rare earth complex oxides as active components of a catalyst have attracted wide attention due to their catalytic oxidizing function for carbon monoxide and hydrocarbons. The Tang et al. patent further states that catalysts using perovskite-type complex oxides as the active components are generally carried on .gamma.-AL.sub.2 O.sub.3. These supports are noted to envitably react chemically with the complex oxide. As a result, aluminum-containing perovskite or aluminum-containing spinel with non-catalytic activity is formed, causing part of the active components to be damaged, so that the activity of the catalysts dropped universally. Attempts have been made to solve the problem by precoating or using the active components as catalysts alone without support. The Tang et al. patent solves these problems by using a support with mullite as a main phase for a perovskite-type active component having the following general formula: EQU {[A.sub.1-x A'.sub.x ].sub.1-y .quadrature..sub.y }{B.sub.1-z B'.sub.z ].sub.1-w .quadrature..sub.w }O.sub.3-.delta.
wherein A represents a rear earth metal element, preferably La, Ce or mixed rare earths and most preferably, La or Ce; A' represents an alkaline earth metal element, preferably Ca, Sr or Ba and most preferably Ca or Sr, .quadrature. represents the vacancy in the structure; B and B' represent the transition metal elements, preferably Ti, Cr, Co, Mn, Cu, Fe or Ni, and most preferably Ti, Cr, Co or Mn; 0.ltoreq.x.ltoreq.0.9; 0.ltoreq.y.ltoreq.0.2; 0.ltoreq.z.ltoreq.0.9; 0.ltoreq.w.ltoreq.0.05; 0.ltoreq..delta..ltoreq.0.8. And a support with mullite as the main phase, wherein the said active components are carried directly on the said support.
U.S. Pat. No. 3,897,367 to Lauder discloses metal oxide catalytic compounds which are also of the perovskite-type ABO.sub.3 structure wherein 1-20% of the B site cations are ruthenium or platinum. The composition of the Lauder patent is an improvement over rare earth cobaltite catalytic compositions.
The present invention is an improvement over both the Tang et al. and Lauder patents.
The catalytic additive of the invention does not require mullite nor a noble metal for catalyzing the conversion of carbon monoxide to carbon dioxide in the regenerator of an FCC unit. The inventive catalytic additive is less expensive to produce and results in an additive with the same efficiency as a noble metal additive in converting the carbon monoxide into carbon dioxide. The combination of elements on a support which does not have mullite as its main phase, e.g., an alumina microsphere, is a very effective "combustion promoter" additive, effectively reducing NOX emissions.